Explosion-proof cathode-ray tubes

ABSTRACT

An explosion-proof cathode-ray tube has an anti-explosion device made as an annular frame which is mounted onto the tube envelope at a critical zone thereof so that there is a gap therebetween which is filled with a self-expanding filler. The frame is provided with a flange, contacting the envelope at the side of the tube screen along the whole of its perimeter, and having a recess facing the surface of the envelope that corresponds to the critical zone of the envelope. The recess has a special profile designed in a manner ensuring a counterbalancing of axial tensions occuring in the tube envelope in its critical zone.

United States Patent [191 Kaljuko et a1.

[451 Sept. 10,1974

[ EXPLOSION-PROOF CATHODE-RAY TUBES [22] Filed: Nov. 6, 1973 [21] Appl.No.: 413,331

Related U.S. Application Data [63] Continuation of Ser. No. 325,127,Jan. 19, 1973, abandoned, which is a continuation of Ser. No. 187,274,Oct. 7, 1971, abandoned.

[30] Foreign Application Priority Data Oct. 27, 1970 U.S.S.R 1481151Dec. 19, 1970 U.S.S.R 1496301 [52] U.S. Cl l78/7.8, l78/7.82, 220/2.l A

[51] Int. Cl H01j 31/08, HOlk l/28 [58] Field of Search l78/7.8, 7.82;220/21 A, 220/23 A [56] References Cited UNITED STATES PATENTS 3,278,68210/1966 Panis 178/7.8

3,314,566 4/1967 Minneman 220/2.1 A

3,558,818 1/1971 DeBoer 178/7.82

Primary Examiner-Howard W. Britton Attorney, Agent, or Firm-Holman &Stern [5 7] ABSTRACT An explosion-proof cathode-ray tube has anantiexplosion device made as an annular frame which is mounted onto thetube envelope at a critical zone thereof so that there is a gaptherebetween which is filled with a self-expanding filler. The frame isprovided with a flange, contacting the envelope at the side of the tubescreen along the whole of its perimeter, and having a recess facing thesurface of the envelope that corresponds to the critical zone of theenvelope. The recess has a special profile designed in a manner ensuringa counterbalancing of axial tensions occuring in the tube envelope inits critical zone.

4 Claims, 6 Drawing Figures EXPLOSION-PROOF CATHODE-RAY TUBES PRIORAPPLICATIONS BACKGROUND OF THE INVENTION The present invention relatesto electron vacuum devices and, in particular, to cathode-ray tubesprovided with anti-explosion devices.

Known in the art are cathode-ray tubes with antiexplosion devices,embracing the tube envelope along its critical zone and having the shapeof a frame mounted onto the envelope with a gap to be filled with afiller, the frame being provided with a flange contacting the envelopeon the side of the tube screen along the whole of its perimeter. Hence,the tube envelope is made explosion-proof with the help of a framehaving a flange and with the help of a filler stuck into the gap betweenthe frame and the envelope.

Such a cathode-raytube with an anti-explosion device comprises asingle-ribbon frame of variable thickness or a multi-ribbon frame weldedof a number of separate ribbons which is tightly pulled onto the sidesurface of the tube envelope over its critical zone so that between theframe and the envelope there would be a gap to be filled with a filler.However, the combined action of the metal frame and the tiller of suchan anti-explosion device is exploited incompletely and does not ensurecomplete explosion-protection of said cathode-ray tubes. Additionally,the metal consumption of such frames is rather high and amounts to 5-15percent.

The above anti-explosion devices for cathode-ray tubes do not ensure therequired degree of explosion protection since they do not providesufficient compensation for maximum axial tensil forces in the criticalzone of the envelope.

SUMMARY OF THE INVENTION tube having an anti-explosion device, embracingthe tube envelope along its critical zone and which has the shape of aframe mounted onto the envelope with a gap' to be filled with a filler,the frame being provided with a flange contacting the tube envelope onthe side of the shape of an arc;

tube screen along the whole of its perimeter, further,

according to the invention, the frame has a recess in its surface facingthe tube envelope in the critical zone of the latter. The frame is alsodesigned so as to compensate for the axial tensile stresses occuring inthe tube envelope in its critical zone.

It is preferred that the frame of the anti-explosion device should bedesigned with a recess having the cross sectional shape of an arc.

In another embodiment of the invention the frame of the anti-explosiondevice is preferably designed with a recess having the cross sectionalshape of an angle.

In a further embodiment of the invention the frame of the anti-explosiondevice is preferably designed with a recess of a rectangular crosssection.

The invention provides tubes having reliable explosion protection andmakes possible reduction of material and of labor consumption requiredfor the manufacturing of cathode-ray tubes with anti-explosion devices.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be betterunderstood from the description of an embodiment given by way of examplewith reference to the accompanying drawings, in which:

FIG. 1 shows the general view of a cathode-ray tube with ananti-explosiondevice according to the invention illustrating the tubeenvelope in part-section;

FIG. 2 is a view similar to that of FIG. 1, but viewed from above;

FIG. 3 is a view showing the section along III-III as in FIG. 2;

F IG. 4 is a view showing the section along IV-IV as in FIG. 2;

FIG. 5 shows a part-section the second version of the anti-explosiondevice made with a recess having the FIG. 6 shows the third version ofthe anti-explosion device made with a recess of a rectangular shape(longitudinal section).

The cathode-ray tube, according to the invention, is provided with ananti-explosion device 1 (FIG. 1) made as a single-ribbon annular frame 2of constant thickness which follows the contour of the periphery of thetube screen and which is mounted on the side surface of the tube in thecritical zone of the envelope 3 corresponding to the rim of the screenand to the area where the screen is attached to the tube cone. The frame2 has a channel like recess 4 of rectangular cross section running alongthe whole of its perimeter.

The recess 4 tapers upwards along the height of the frame 2 to form aflange 5 constituting the upper part of the frame. The contact betweenthe frame 2 and the side surface of the tube is effected through theflange 5 (FIG. 2), the perimeter of which is somewhat less than that ofthe tube envelope 3 (FIG. 1) along the line of contact, due to which acertain amount of tensile stress in the critical zone of the tubeenvelope is counter-balanced. The frame 2 can practically embrace thewhole critical zone of the tube envelope 3. It is mounted on the sidesurface of the tube so that the recess 4 faces the critical zone in theregion of maximum stress to which the tube envelope 3 is subjected. Whenthe frame 2 is tightly pulled over the envelope a gap appears adjacentthe line of contact between the frame and the side surface of the tube.The gap is then filled with a self-expanding tiller 6, eg withalebaster.

The distribution of tensile stresses in the critical zone of the tubeenvelope 3 is not'uniform along its perimeter. The maximum tensilestress occurs in the corners of the screen and decreases towards thecenters of its sides. To counterbalance the stress in the critical zoneof the envelope 3 in a uniform manner the frame 2 is made so that theangle a of the flange 5 is variable along the perimeter of the frame 2in contrast to known anti-explosion devices. The value of the angle a isse lected in accordance with the amount of tensile stress to becountered and can vary from 3 to When the tube has a round screen theangle a of the flange will be constant and will be selected within theabove range depending on the value of axial tensile stress in the tubeenvelope 3.

FIG. 3 illustrates a section of the tube envelope 3 with theanti-explosion device 1, the section being made along the IIIIII line asin FIG. 2. The angle a, of the flange 5 is minimum; it is selected from3 and higher. It is preferable that the angle a, be selected betweenand.20.

FIG. 4 illustrates a section of the tube envelope with theanti-explosion device 1, the section being made along the lV-IV line asin FIG. 2. The maximum angle a is selected to be 90 and lower. It ispreferable that the 0: angle be selected between 45 and 50.

The maximum tensile forces in the critical zone of the tube envelope 3are counterbalanced by the total action of all compensation forces.These are: the tightness of the frame 2 caused by the elasticdeformation of the flange 5 and the expansion of the filler 6 affectingthe envelope 3 right in its critical zone. Here, the thickness of thefiller 6 layer and the counterbalance force produces depend upon therecess 4. Additional compression of the envelope 3 is caused also by theelastic properties of the frame 2 manifested through its co-action withthe self-expanding filler 6.

The recess 4 in the frame 2 can be of various shapes depending upon theapplication of the cathode-ray tube having the anti-explosion device 1.

Illustrated in FIG. 5 is a section of a cathode-ray tube with theanti-explosion device 1 whose frame 2 is provided with a recess 7 havingthe shape of an arc.

FIG. 6 shows a section of a cathode-ray tube with the anti-explosiondevice I provided with a recess 8 having the shape of an angle.

The anti-explosion device protects the cathode-ray tube from anaccidental explosion caused by a defect in the envelope 3 as well asfrom an explosion caused by a mechanical damage of the tube envelope 3.It is most preferable to use the anti-explosion devices 1 of the typedescribed herein with larger cathode-ray tubes that might explode with agreat force. The employment of the present antiexplosion device 1 makesit possible to practically avoid explosions.

The anti-explosion device 1 is mounted onto the envelope 3 of acathode-ray tube in the following way.

The frame 2 having a substantially rectangular recess 4 and a flange 5whose angle 0: with the tube envelope varies along the perimeter of theframe 2 from to 45, is pulled tightly with the force of 2-3 tonnes overthe side surface of the tube envelope 3. The frame 2 is mounted in sucha way that the recess 4 should be opposite the area of maximum stress inthe critical zone of the tube envelope 3. The gap that is formed betweenthe side surface of the envelope 3 and the frame 2 is filled with analebaster mixture of definite concentration ensuring that the whole ofthe gap is tightly filled. In the course of solidification thealebaster, which has adhesive properties, expands and compresses theenvelope 3 counterbalancing the stress in its critical zone. Undernormal conditions the initial process of alebaster solidification lasts15-20 min. At higher temperatures however; this process can beaccelerated. The explosion-proof action of the anti-explosion device 1is fully effective only after the process of complete solidification ofthe alebaster material is over, which, under normal conditions, takesabout 24 hours.

The cathode-ray tube with the anti-explosion device described aboveincreases the efficiency of explosion protection and ensures savings inlabour and materials during tube manufacture.

What is claimed is:

1. An explosion-proof cathode-ray tube comprising:

an envelope having a screen portion and a core portion;

an anti-explosion means embracing the surface of said envelope in acritical zone, which zone defines a region where said screen portion isattached to said cone portion; and

a frame means of said anti-explosion means peripherally mounted on saidsurface of said envelope so that a gap is formed between said frame andsaid envelope, which gap is filled with a consolidated filler material,said frame means having a flanged portion and a recessed portion, saidflanged portion tensionally contacting the perimeter of said screenportion of said envelope in the vicinity of said critical zone, saidrecessed portion facing the surface of said screen portion of saidenvelope along said critical zone and having a constant cross-sectionalshape around said frame perimeter so as to counter-balance together withsaid tensionally contacting flanged portion, axial tensile stresseswhich occur in said critical zone. 2. A cathode-ray tube as claimed inclaim 1, wherein said recess is are shaped in cross-section.

3. A cathode-ray tube as claimed in claim 1, wherein said recess has anangle-shaped cross-section.

4. A cathode-ray tube as claimed in claim 1, wherein said recess has arectangular cross section.

1. An explosion-proof cathode-ray tube comprising: an envelope having ascreen portion and a core pOrtion; an anti-explosion means embracing thesurface of said envelope in a critical zone, which zone defines a regionwhere said screen portion is attached to said cone portion; and a framemeans of said anti-explosion means peripherally mounted on said surfaceof said envelope so that a gap is formed between said frame and saidenvelope, which gap is filled with a consolidated filler material, saidframe means having a flanged portion and a recessed portion, saidflanged portion tensionally contacting the perimeter of said screenportion of said envelope in the vicinity of said critical zone, saidrecessed portion facing the surface of said screen portion of saidenvelope along said critical zone and having a constant cross-sectionalshape around said frame perimeter so as to counter-balance together withsaid tensionally contacting flanged portion, axial tensile stresseswhich occur in said critical zone.
 2. A cathode-ray tube as claimed inclaim 1, wherein said recess is arc shaped in cross-section.
 3. Acathode-ray tube as claimed in claim 1, wherein said recess has anangle-shaped cross-section.
 4. A cathode-ray tube as claimed in claim 1,wherein said recess has a rectangular cross section.